| 1. |
- Abtahi, Jahan, et al.
(författare)
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A bisphosphonate-coating improves the fixation of metal implants in human bone. A randomized trial of dental implants
- 2012
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Ingår i: Bone. - : Elsevier. - 8756-3282 .- 1873-2763. ; 50:5, s. 1148-1151
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Tidskriftsartikel (refereegranskat)abstract
- Many surgical procedures use metal implants in bone. The clinical results depend on the strength of the bone holding these implants. Our objective was to show that a drug released from the implant surface can improve parameters reflecting the quality or amount of this bone. Sixteen patients received paired dental titanium implants in the maxilla, in a randomized, double-blinded fashion. One implant in each pair was coated with a thin fibrinogen layer containing 2 bisphosphonates. The other implant was untreated. Fixation was evaluated by measurement of resonance frequency (implant stability quotient; ISQ) serving as a proxy for stiffness of the implant-bone construct. Increase in ISQ at 6 months of follow-up was the primary variable. None of the patients had any complications. The resonance frequency increased 6.9 ISQ units more for the coated implants (p = 0.0001; Cohens d = 1.3). The average difference in increase in ISQ and the effect size, suggested a clinically relevant improvement. X-ray showed less bone resorption at the margin of the implant both at 2 months (p = 0.012) and at 6 months (p = 0.012). In conclusion, a thin, bisphosphonate-eluting fibrinogen coating might improve the fixation of metal implants in human bone. This might lead to new possibilities for orthopedic surgery in osteoporotic bone and for dental implants.
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| 4. |
- Agholme, Fredrik, et al.
(författare)
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The effects of Dickkopf-1 antibody on metaphyseal bone and implant fixation under different loading conditions
- 2011
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Ingår i: BONE. - : Elsevier Science B.V., Amsterdam.. - 8756-3282. ; 48:5, s. 988-996
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Tidskriftsartikel (refereegranskat)abstract
- The secreted protein Dickkopf-1 (Dkk1) is an antagonist of canonical Wnt signaling, expressed during fracture healing. It is unclear how it is involved in the mechanical control of bone maintenance. We investigated the response to administration of a Dkk1 neutralizing antibody (Dkk1-ab) in metaphyseal bone under different loading conditions, with or without trauma. In this three part experiment, 120 rats had a screw or bone chamber inserted either unilaterally or bilaterally in the proximal tibia. Mechanical (pull-out) testing, mu CT and histology were used for evaluation. The animals were injected with either 10 mg/kg Dkk1-ab or saline every 14 days for 14, 28, or 42 days. Antibody treatment increased bone formation around the screws and improved their fixation. After 28 days, the pull-out force was increased by over 100%. In cancellous bone, the bone volume fraction was increased by 50%. In some animals, one hind limb was paralyzed with Botulinum toxin A (Botox) to create a mechanically unloaded environment. This did not increase the response to antibody treatment with regard to screw fixation, but in cancellous bone, the bone volume fraction increased by 233%. Thus, the response in unloaded, untraumatized bone was proportionally larger, suggesting that Dkk1 may be up-regulated in unloaded bone. There was also an increase in thickness of the metaphyseal cortex. In bone chambers, the antibody treatment increased the bone volume fraction. The results suggest that antibodies blocking Dkk1 might be used to stimulate bone formation especially during implant fixation, fracture repair, or bone disuse. It also seems that Dkk1 is up-regulated both after metaphyseal trauma and after unloading, and that Dkk1 is involved in mechano-transduction.
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| 6. |
- Aspenberg, Per, et al.
(författare)
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Targeting RANKL for reduction of bone loss around unstable implants: OPG-Fc compared to alendronate in a model for mechanically induced loosening
- 2011
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Ingår i: BONE. - : Elsevier Science B.V., Amsterdam.. - 8756-3282. ; 48:2, s. 225-230
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Tidskriftsartikel (refereegranskat)abstract
- Orthopedic joint prostheses may loosen because of localized bone resorption. Despite initial optimism, there are no reports showing that bisphosphonates can stop the progression of prosthetic loosening once it has begun. This might be due to the strong resorptive stimulus, which continuously recruits new osteoclasts. Therefore, we hypothesized that a treatment targeting osteoclast recruitment would be more efficacious than a treatment reducing osteoclast activity. We used a previously described rat model for instability-induced bone resorption, and compared OPG-Fc with alendronate at a clinically relevant or an extreme dose. A titanium plate was osseointegrated at the rat tibial surface. Instability was simulated by a piston, moving perpendicularly to the bone surface. Piston movement induced bone loss via hydrostatic pressure or fluid flow. Rats were randomized to 5 groups (total n = 56), of which 4 were subjected to instability and one was stable. The unstable groups were injected with either high-dose OPG-Fc (10 mg/kg, twice weekly), a high dose of alendronate (20 mu g /kg/day), an extreme dose of alendronate (200 mu g/kg/day) or saline. Significant protection against resorption could only be shown for OPG-Fc and the extreme alendronate dose. Both alendronate doses reduced serum levels of tartrate-resistant acid phosphatase isoform 5b to a similar extent, demonstrating that the lower dose was able to reduce resorption in the normally remodeling skeleton, although not in the osteolytic lesions caused by instability. Osteoclast numbers in the lesion were increased by the lower bisphosphonate dose and reduced by OPG-Fc. The results suggest the possibility of targeting osteoclast recruitment via the RANKL system in patients with impending prosthetic loosening.
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| 7. |
- Goldhahn, Jörg, et al.
(författare)
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Clinical evaluation of medicinal products for acceleration of fracture healing in patients with osteoporosis
- 2008
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 43:2, s. 343-347
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Tidskriftsartikel (refereegranskat)abstract
- Pre-clinical studies indicate that pharmacologic agents can augment fracture union. If these pharmacologic approaches could be translated into clinical benefit and offered to patients with osteoporosis or patients with other risks for impaired fracture union (e.g. in subjects with large defects or open fractures with high complication rate), they could provide an important adjunct to the treatment of fractures. However, widely accepted guidelines are important to encourage the conduct of studies to evaluate bioactive substances, drugs, and new agents that may promote fracture union and subsequent return to normal function. A consensus process was initiated to provide recommendations for the clinical evaluation of potential therapies to augment fracture repair in patients with meta- and diaphyseal fractures. Based on the characteristics of fracture healing and fixation, the following study objectives of a clinical study may be appropriate: a) acceleration of fracture union, b) acceleration of return to normal function and c) reduction of fracture healing complications. The intended goal(s) should determine subsequent study methodology. While an acceleration of return to normal function or a reduction of fracture healing complications in and of themselves may be sufficient primary study endpoints for a phase 3 pivotal study, acceleration of fracture union alone is not. Radiographic evaluation may either occur at multiple time points during the healing process with the aim of measuring the time taken to reach a defined status (e.g. cortical bridging of three cortices or disappearance of fracture lines), or could be obtained at a single pre-determined timepoint, were patients are expected to reach a common clinical milestone (i.e. pain free full weight-bearing in weight-bearing fracture cases). Validated Patient Reported Outcomes (PRO's) measures will need to support the return to normal function co-primary endpoints. If reduction of complication rate (e.g. non-union) is the primary objective, the anticipated complications must be defined in the study protocol, along with their possible associations with the specified fracture type and fixation device. The study design should be randomized, parallel, double-blind, and placebo-controlled, and all fracture subjects should receive a standardized method of fracture fixation, defined as Standard of Care. © 2008 Elsevier Inc. All rights reserved.
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| 8. |
- Goldhahn, Joerg, et al.
(författare)
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Evidence for anti-osteoporosis therapy in acute fracture situations-Recommendations of a multidisciplinary workshop of the International Society for Fracture Repair
- 2010
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Ingår i: BONE. - : Elsevier BV. - 8756-3282. ; 46:2, s. 267-271
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Tidskriftsartikel (refereegranskat)abstract
- The International Society for Fracture Repair convened a multidisciplinary workshop to assess the current evidence around the interaction between anti-osteoporosis drugs and the healing of incident fractures, with a view to making recommendations for clinical practice. The consensus was that there is no evidence-based reason to withhold anti-resorptive therapy while a fracture heals, whether or not the patient was taking such therapy when the fracture occurred. The workshop also considered existing models of service provision for secondary prevention and concluded that the essential ingredient for reliable delivery is the inclusion of a dedicated coordinator role. Several unresolved issues were defined as subjects for further research, including the question of whether continuous long-term administration of anti-resorptives may impair bone quality. The rapidly changing area requires re-assessment of drugs and their interaction with fracture healing in the near future.
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| 9. |
- Gustafsson, Anna, et al.
(författare)
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Strains caused by daily loading might be responsible for delayed healing of an incomplete atypical femoral fracture
- 2016
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Ingår i: Bone. - : ELSEVIER SCIENCE INC. - 8756-3282 .- 1873-2763. ; 88, s. 125-130
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Tidskriftsartikel (refereegranskat)abstract
- Atypical femoral fractures are insufficiency fractures in the lateral femoral diaphysis or subtrochanteric region that mainly affect older patients on bisphosphonate therapy. Delayed healing is often seen in patients with incomplete fractures (cracks), and histology of bone biopsies shows mainly necrotic material inside the crack. We hypothesized that the magnitude of the strains produced in the soft tissue inside the crack during normal walk exceeds the limit for new bone formation, and thereby inhibit healink. A patient specific finite element model was developed, based on clinical CT images and high resolution CT images of a biopsy from the crack site. Strain distributions in the femur and inside the crack were calculated for load cases representing normal walk. The models predicted large strains inside the crack, with strain levels above 10% in more than three quarters of the crack volume. According to two different tissue differentiation theories, bone would only form in less than 1-5% cif the crack volume. This can explain the impaired healing generally seen in incomplete atypical fractures. Furthermore, the microgeometry of the crack highly influenced the strain distributions. Hence, a realistic microgeometry needs to be considered when modeling the crack. Histology of the biopsy showed signs of remodeling in the bone tissue adjacent to the fracture line, while the crack itself contained mainly necrotic material and signs of healing only in portions that seemed to have been widened by resorption. In conclusion, the poor healing capacity of incomplete atypical femoral fractures can be explained by biomechanical factors, and daily low impact activities are enough to cause strain magnitudes that prohibit bone formation. (C) 2016 Elsevier Inc. All rights reserved.
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